er part of the stomach. It has a
length of six or eight inches and weighs from two to three and one half
ounces. Its secretion, the pancreatic juice, is emptied into the duodenum
by a duct which, as a rule, unites with the duct from the liver.

*The Pancreatic Juice* is a colorless and rather viscid liquid, having an
alkaline reaction. It consists of about 97.6 per cent of water and 2.4 per
cent of solids. The solids include mineral salts (the chief of which is
sodium carbonate) and four different chemical agents, or enzymes,--trypsin,
amylopsin, steapsin, and a milk-curding enzyme. These active constituents
make of the pancreatic juice the most important of the digestive fluids.
It acts with vigor on all of the nutrients insoluble in water, producing
the following changes:

1. It converts the starch into maltose, completing the work begun by the
saliva. This action is due to the _amylopsin_,(61) which is similar to
ptyalin but is more vigorous.

2. It changes proteids into peptones and proteoses, completing the work
begun by the gastric juice. This is accomplished by the _trypsin_, which
is similar to, but more active than, the pepsin.

3. It digests fat. In this work the active agent is the _steapsin_.

The necessity of a milk-curding enzyme, somewhat similar to the rennin of
the gastric juice, is not understood.

*Digestion of Fat.*--Several theories have been proposed at different times
regarding the digestion and absorption of fat. Among these, what is known
as the "solution theory" seems to have the greatest amount of evidence in
its favor. According to this theory, the fat, under the influence of the
steapsin, absorbs water and splits into two substances, recognized as
glycerine and fatty acid. This finishes the process so far as the
glycerine is concerned, as this is soluble in water; but the fatty acid,
which (from certain fats) is insoluble in water,(62) requires further
treatment. The fatty acid is now supposed to be acted on in one, or both,
of the following ways: 1. To be dissolved as fatty acid by the action of
the bile (since bile is capable of dissolving it under certain
conditions). 2. To be converted by the sodium carbonate into a form of
soap which is soluble in water.

The emulsification of fat is known to occur in the small intestine. By
this process the fat is separated into minute particles which are
suspended in water, but not changed chemically, the mixture being known as
an _emulsion_. W